S. Mike Linhart and Kris D. Lund2006Upper Gar Lake Boundary (polygon) - Edge of water at lake-surface elevation, 1394.7 ft above NGVD 29vector digital dataScientific Investigations Map2006-2949-FRaleigh, NCU.S. Geological Surveyhttps://water.usgs.gov/lookup/getspatial?sim06-2949F_ugar_bndryS. Mike Linhart and Kris D. Lund2006Bathymetric Contour Maps of Lakes Surveyed in Iowa in 2004pdf documentScientific Investigations Map2006-2949Raleigh, NCU.S. Geological Surveyhttp://pubs.water.usgs.gov/sim2006-2949This data set consists of digital polygon coverage that defines the shoreline of Upper Gar Lake in Dickinson Co., Iowa. The U.S. Geological Survey conducted a bathymetric survey of Upper Gar Lake in 2004.This digital, geographically referenced data set was developed by the U.S. Geological Survey to be used with the Lake Bathymetric project, Eastern Field Unit, Iowa City, Iowa.This coverage was used to define the boundary during generation of the bathymetric three-dimensional surface. To define the shoreline, point locations around the lake were collected with a bow-mounted GPS antenna by touching the bow of the boat to the shoreline. The data points were input into a geographic information system (GIS) software package, ArcInfo, to create a point coverage representing discrete point locations. The polygon coverage defining the shoreline was created in ArcInfo by connecting the point locations in the point coverage. Digital orthophoto quads (DOQ's) were used as an aid in adjusting the coverage of the shoreline.2004ground conditionCompleteNone planned
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43.363872NoneLakesBathymetryInlandWatersHydrologyUSGSNoneUpper Gar LakeDickinson CountyIowaThis digital, geographically referenced data set was developed by the U.S. Geological Survey to be used with the Lake Bathymetric project, Eastern Field Unit, Iowa City, Iowa.The data are released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use.U.S. Geological SurveyGreg NalleyProject Chief - Eastern Field Unit Supervisory Hydrologistmailing addressP.O. Box 1230Iowa CityIowa52244USA319-337-4191319-358-3606gmnalley@usgs.govCompilation of this data set prepared in cooperation with Iowa Department of Natural Resources.Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.1.0.722Topologically CleanPolygon coverage created in ArcEdit by digitizing the arc vertices corresponding to the surveyed shore points locations in the underlying ugar_edgepts coverage. This coverage defines the shoreline of the lake for generating the contour map. Digital orthophoto quads (DOQ's) were later used as an aid in further adjusting the coverage of the shoreline.Accuracy is tested by visual comparison of source with digital data on an interactive computer system.Iowa Department of Natural ResourcesUnknownDigital Orthophoto Quad2002remote-sensing imagehttp://www.igsb.uiowa.edu/nrgislibx/Aerial Photo2002ground conditionNoneDigital orthophoto quads (DOQ's) were used in further adjusting and smoothing the coverage of the lake boundary. The coverage was overlain on the DOQ and additional vertices were digitized into the arcs at locations corresponding the shoreline shown on the DOQ.Water-surface elevation: Initial measurements determined the elevation of the water surface of Upper Gar Lake referenced to National Geodetic Vertical Datum (NGVD) of 1929 using standard surveying techniques. A reference point (point from which to measure the water surface) elevation was established by leveling from a nearby existing reference mark with a known elevation (provided by Dickinson County Engineers Office). Accuracy of the existing reference mark is unknown. The reference point is located on the concrete outflow structure at the road junction at the lower end of Lower Gar Lake. The elevation of the reference point was found to be 1399.804 ft above NGVD29. The elevation of the reference point was verified by a static GPS survey (using the Ashtech GPS system) with a difference of 0.063 ft. Measuring from the reference point (using a steel tape), the water-surface elevation was found to be 1394.7 ft above NGVD29 on June 8, 2004.2004Data collection: Bathymetry data were collected using the Bathymetric Survey System (BSS+5) with a 200-kHZ intelligent depth sounder (IDS) and a differential GPS (Novatel DGPS beacon or omnistar receiver) (Specialty Devices, Inc., 2003, Bathymetric Survey System BSS+5 with omnistar manual: Specialty Devices, Inc., Plano, Texas, 38 p.). The depth sounder emits pulses of sound that are reflected off the lake bottom and are received by a transducer. The differential GPS has a horizontal accuracy of about 1 meter (3.281 ft). Bathymetry and position data were collected and stored in Hypack Max software (ver. 2.12a) (Hydrographic Survey Software, User's Manual, Hypack Max, Coastal Oceanographics, Inc., Middlefield, Conn.). In Hypack Max, the geodetic parameters were set to UTM north, Zone 15, and ellipsoid GRS-1980. Distance (easting and northing) and depth units were both collected in feet. Current limitations of the Bathymetric Survey System (BSS+5) restrict data collection to depths greater than approximately 3.3 ft.
A bar check calibration on the echo sounder was performed at the start of each day following established protocols (U.S. Army Corps of Engineers, 1994, Engineering and design: Hydrographic survey EM 1110-2-1003, chap. 9-3, p. 9-4 to 9-9). This was done to ensure that the echo sounder was calibrated correctly. The bar check involves suspending a 2-ft-diameter flat aluminum plate directly below the echo sounder. The suspension line is marked in 5-ft increments. An initial calibration is made at 5 ft by entering the speed of sound in water (based on water temperature) and then adjusting the offset of the transducer in the computer software. The offset is the draft of the transducer below the lake surface. The aluminum plate is then lowered in 5-ft increments (depending on the range of depths expected to be encountered on the day of data collection) and adjustments in the speed of sound are made until depth readings and the depth of the aluminum plate agree to within approximately 0.1 ft.
Bathymetry data were collected along planned transect lines that were set-up in Hypack Max using the internal line editor prior to data collection. Transect lines were spaced at 75-ft intervals perpendicular to the long axis of Upper Gar Lake. Depending on boat speed, bathymetry data points were collected at approximately 5- to 10-ft intervals. Data points may be much closer in areas where transect or perimeter runs overlap. Bathymetry data points also were collected while driving the boat once around the perimeter of the lake. The distance of the boat from shore during the perimeter run varied, depending upon the depths encountered, due to the depth limitations of the data-collection equipment. The raw bathymetry data were recorded in Hypack Max as depths (in feet below water surface to the lake bottom). Target points were collected in areas of the lake where it was too shallow to collect data with the BSS+5 system. Target point depths were collected manually, using a measuring device marked in 0.10-ft increments, along with a corresponding easting and northing location. Depending on lake-bottom type and surface conditions of the lake, accuracy of these measurements can vary between 0.05 ft and 0.5 ft. The number and location of target points were based on a judgment made in the field that was thought to be spatially representative of the area. In addition, shore point locations (easting and northing) were collected to define the shoreline of the lake. These locations are collected by touching the bow of the boat to the shoreline at various intervals along the shoreline and recording the position using a bow-mounted GPS antenna.
An independent bathymetry data set (in the coverage ugar_ctrlpts) also was collected over a smaller area of Upper Gar Lake. This control data set was used to estimate precision (repeatability) of the sounding data collected with the echo sounder. For Upper Gar Lake, there were 13 paired data and control points that were located within 1.5 ft of each other with a calculated Root Mean Square Error (RMSE) of 0.47 ft. The control data set also is used to estimate the accuracy of the produced contours.2004Post-processing: Bathymetry data were processed using the Hypack Max software. Post-processing involved removing obvious spikes, inputting depths for the time-tagged target points, and editing extraneous points within the shore point files. Due to extensive aquatic vegetation in Upper Gar lake at the time of the survey, many spikes in the raw bathymetry data along several transects were deleted during the initial processing. In addition, tide corrections were applied in Hypack Max to convert raw sounding depths to elevation. The tide file subtracts the depths from the assigned lake-surface elevation (obtained from measurement from reference point elevation to lake water surface). The processed bathymetry data in Hypack Max were sorted and exported to XYZ format. The perimeter and transect bathymetry data were weeded (thinned) to reduce the density of points in one direction (along data-collection transects) to minimize the spatial pull of contours toward the densified lines. Of the original 1,235 data points, 631 data points remained. A total of three separate files were exported into XYZ format: (1) transect and perimeter bathymetry data; (2) shore point location data; and (3) the target point data. The XYZ files were then converted to ASCII text files for input into ESRI-ArcGIS (ver. 8.3). The perimeter and transect data were combined into one data set (ugar_allpts.txt). The file ugar_allpts.txt contains all processed data points (not weeded) exported from Hypack Max (not including edge and target points).2004-2005Generation of Bathymetry Map: The output text files (containing northing, easting, and elevation) were input into an arc macro language (AML) script called CREATEPOINT in ARC to generate three corresponding coverages (ugar_edgepts, ugar_tinpts, and ugar_targpts). The ugar_edgepts coverage contains the shore point locations. The ugar_tinpts coverage contains the weeded bathymetry points collected with the depth sounder. The ugar_targpts coverage contains the bathymetry target points collected manually. The projections for the coverages were then defined in ARC as UTM zone 15, NAD83, and units in feet. Some points in the ugar_targpts coverage were deleted because the locations were in areas of the lake where bathymetry data were already collected. The coverage ugar_allpts contains unweeded bathymetry points generated from the ugar_allpts.txt file.
A polygon coverage (ugar_bndry) was created for the lake shore by first connecting (digitizing in ArcEdit) the points in the ugar_edgepts coverage. Digital orthophoto quads (DOQ's) (Iowa Department of Natural Resources, 2002-2003, Iowa 2002 Digital Orthophoto Update Project, information available on World Wide Web at URL http://www.igsb.uiowa.edu/nrgislibx/) were later used as an aid in further adjusting the coverage of the shoreline. From the polygon coverage ugar_bndry, a line coverage (ugar_bndelev) was created in ARC. An elevation field (elev) was then added to the attribute table of the ugar_bndelev coverage (ugar_bndelev.aat). In ArcEdit, the "elev" field of this coverage was set to a value of 1394.7 ft (lake-surface elevation). The coverages (ugar_bndry and ugar_bndelev) were defined in ARC as UTM zone 15, NAD83, with units in feet.
To generate contours and calculate lake volume, three-dimensional surfaces (TIN models) were created using 3-D Analyst in ArcMap. The TIN (ugar_tin4) model was generated to create the preliminary contours. The point coverages, ugar_tinpts and ugar_targpts, were input into ugar_tin4 and triangulated as mass points. Height source was the "elevation" field in the point coverage attribute table. The ugar_bndelev line coverage was input as a hard line using the "elev" field as the height source (elevation value = 1394.7 ft). A shapefile (ugar_breaklines) was input as a soft line. The ugar_bndry coverage (polygon) was input as a hard clip to clip the TIN to the lake shoreline. Another TIN model (ugar_tinsmooth) was later generated to re-calculate lake volume after the boundary coverages (ugar_bndry and ugar_bndelev) were further adjusted using DOQ's.2005-2006VectorComplete chain1Label point1GT-polygon composed of chains1Transverse Mercator0.999600-93.0000000.0000001640416.6666670.000000coordinate pair0.0000180.000018survey feetNorth American Datum of 1983Geodetic Reference System 806378137.000000298.257222National Geodetic Vertical Datum of 19290.1feetImplicit coordinate
ugar_bndry.patPolygon Attribute TableARC/INFO(R) GIS SoftwareFIDInternal feature number.ESRISequential unique whole numbers that are automatically generated.ShapeFeature geometry.ESRICoordinates defining the features.AREAArea of feature in internal units squared.ESRIPositive real numbers that are automatically generated.PERIMETERPerimeter of feature in internal units.ESRIPositive real numbers that are automatically generated.UGAR_BNDRY#Internal feature number.ESRISequential unique whole numbers that are automatically generated.UGAR_BNDRY-IDUser-defined feature number.ESRIIntegern/an/aU.S. Geological SurveyAsk USGS - Water Webserver Teammailing address445 National CenterRestonVA20192USA1-888-275-8747 (1-888-ASK-USGS)http://water.usgs.gov/user_feedback_form.htmlNoneThe Lake Bathymetric project of the Eastern Field Unit, Iowa Water Science Center, the Water Resources Discipline (WRD), and the U.S. Geological Survey make no guarantee nor offer any warranty concerning the accuracy, condition, or application of the information contained in these geographic data.
The burden for determining fitness for use of this data lies entirely with the user. Although these data have been processed successfully on computers of WRD, no warranty, expressed or implied, is made by WRD regarding the use of these data on any other system, nor does the fact of distribution constitute or imply any such warranty.
In no event shall the WRD have any liability whatsoever for payment of any consequential, incidental, indirect, special, or tort damages of any kind, including, but not limited to, any loss of profits arising out of the delivery, installation, operation, or support by WRD.
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.ARCEFull coveragezipped0.028https://water.usgs.gov/GIS/dsdl/sim06-2949F_ugar_bndry.e00.gzNone. This dataset is provided by USGS as a public service.20070130U.S. Geological SurveyAsk USGS -- Water Webserver Teammailing address445 National CenterRestonVA20192USA1-888-275-8747 (1-888-ASK-USGS)https://answers.usgs.gov/cgi-bin/gsanswers?pemail=h2oteam&subject=GIS+Dataset+sim06-2949F_ugar_bndryFGDC Content Standards for Digital Geospatial MetadataFGDC-STD-001-1998local timeNoneNone